Torque transmission mechanisms are used in many applications, such as, for example, in electric powered surgical cutters used in the medical field. Typical transmission mechanisms comprise an output gear connected an output end of a gearbox (e.g., a planetary gearbox) or electric motor, allowing for power from the gearbox or motor to be transferred to an application, such as a blade, fan, or wheel. The output gear may contain connection features in order to connect it to the output end of the gearbox, such as one or more connection holes interfacing with one or more corresponding connection columns connected to the output end of the gearbox.
Due to safety considerations, it is desirable for the output gears of torque transmission mechanisms, such as those used in surgical cutters, to have a high degree of toughness, so that they do not shatter or break when subjected to a large impact. In order to achieve the necessary toughness, the output gears may be manufactured using metal injection molding (MIM), as output gears created in this fashion generally exhibit the toughness necessary to withstand large impacts due to having low internal stress.
However, because MIM causes shrinkage during the manufacturing process, it is often difficult to create connection features (e.g., connection holes) having the precise tolerances needed to interface the output gear with the gearbox or motor. Thus these features typically require secondary processing, adding complexity to the manufacturing process and increasing the cost of the output gears.
Alternatively, powder metallurgy (PM) would enable the connection features to have the desirable tolerance precision without requiring secondary processing, thus lowering the cost and complexity of manufacturing. However, output gears manufactured using powder metallurgy are often too brittle, lacking the toughness required in many applications.
Accordingly, there exists a need for a lower-cost torque transmission mechanism with sufficient toughness and sufficient tolerance precision that is simple to manufacture.